本論文主要著重在金屬氧化物半導體，主要以二氧化鈦(TiO2)奈米線為主，再以相同的成長方式，成長氧化銅(CuO)與氮化鎵(GaN)之奈米線，並且研製和分析其感測器之應用。
首先，我們利用化學氣相沉積(Chemical Vapor Deposition，CVD)於玻璃基板上成長二氧化鈦奈米線，電子顯微鏡(SEM)結果得知，二氧化鈦奈米線平均長寬分別為300 nm與50 nm。在二氧化鈦紫外光檢測器研製方面，所組裝的二氧化鈦奈米線紫外光檢測器其截止波長為390 nm。與傳統的薄膜式二氧化鈦光檢測器相比，二氧化鈦奈米線光檢測器之光電流比薄膜式光檢測器的光電流約增大10倍。在偏壓5 V與390 nm的光照下，所量測到的二氧化鈦奈米線光檢測器與薄膜式二氧化鈦光檢測器的光響應值分別為6.85×10−2與7.65×10−3 mA/W。此外，二氧化鈦奈米線光檢測器的紫外光與可見光拒斥比也比薄膜式二氧化鈦光檢測器的拒斥比大。這是歸因於奈米線有極大的表面積/體積比，在光的吸收上表現得比薄膜來的優異。基於上述結果，我們進一步利用聚乙烯吡咯啶(Polyvinylpyrrolidone, PVP)有機材料當作絕緣層，組裝金屬-絕緣層-半導體(MIS)二氧化鈦奈米線紫外光檢測器。與傳統式的金屬-半導體-金屬(MSM)二氧化鈦奈米線光檢測器相比，在偏壓5 V下，所量測到MIS二氧化鈦奈米線光檢測器與MSM二氧化鈦奈米線光檢測器的暗電流分別為4.95×10−10與9.52×10−10 A，這是由於使用PVP有機材料當作絕緣層可有效的抑制漏電流產生。而在5 V偏壓與390 nm的光照下，所量測到MIS二氧化鈦奈米線光檢測器與MSM二氧化鈦奈米線光檢測器的光電流分別為8.81×10−8與3.02×10−9 A，這是歸因於PVP有機材料中有許多OH鍵結，因此在電極端收集到更多電子。且MIS二氧化鈦奈米線光檢測器與MSM二氧化鈦奈米線光檢測器測得的光響應值分別2.46×10−3與7.08×10−5 A/W。同時，MIS二氧化鈦奈米線光檢測器與MSM二氧化鈦奈米線光檢測器所測得的雜訊等校功率與檢測度分別為7.49×10−12與1.34×10−9 W，8.86×1011與4.97×109 cm•Hz0.5•W−1。這樣的結果也說明所組裝的二氧化鈦奈米線紫外光檢測器，有好的實用性。此外，我們還製作異質結構光二極體方面，p型-氧化銅(Cu2O)濺鍍在n型-二氧化鈦奈米線上且形成異質接面二極體。實驗結果發現，二極體的起始電壓為0.9 V，在10 V偏壓下，二極體反向暗漏電流為3.37×10−8 A，在光照下可得到1.15×10−6 A。
在氣體感測器方面，我們將二氧化鈦奈米線應用於酒精、甲醇、異丙醇與丙酮氣體感測，在偏壓1 V、感測溫度300 °C與氣體濃度100 ppm下，元件的響應分別為85、71、53與45 %。我們發現上述的氣體皆有良好的響應，尤其是酒精表現更優異。以上述的條件為背景，在酒精感測上，當氣體濃度為5、10、30、50、80和100 ppm下，所對應的電流值分別為17、27、60、93、125和191 nA。為提升酒精氣體感測器，我們利用紫外光的照射下，當氣體濃度為5、10、30、50、80和100 ppm下，元件的響應分別為28、30、42、51、67和89 %。在低氣體濃度5 ppm下，相較於未照光下的響應，提升了4倍的響應度。這樣的結果表示所組裝的二氧化鈦奈米線酒精氣體感測器，有良好與靈敏的感測度以及商業化的價值性。
最後，基於上述的實驗成長方法，我們藉由熱氧化法在大氣下成長鋅摻雜氧化銅奈米線，應用於場發射元件。鋅摻雜氧化銅奈米線中，鋅含量約為9.9 %。在場效發射元件，相較於未摻雜的氧化銅奈米線，經實驗發現，鋅摻雜的氧化銅，臨界電場從8.3 V/μm降至4.1 V/μm，功函數也從原先的4.5 eV降至1.54 eV。另外，我們也利用奈米金粒子吸附在氮化鎵奈米線上，增強場發射元件效應。實驗發現，相較於沒有金粒子的氮化鎵奈米線，吸附奈米金粒子的氮化鎵奈米線，臨界電場與功函數分別從8.29 V/μm與4.1 eV降至6.67 V/μm與3.2 eV。這可以歸咎於較大的能帶扭曲和更多的電子積累，使得更多的電子可以從吸附金粒子的氮化鎵奈米線發射。

The main goal of this dissertation is the growth of one-dimensional oxide, including gallium nitride (GaN), copper oxide (CuO) and titanium dioxide (TiO2). Fabricate and analysis of their nanowire-based sensor device applications.
First of all, we were grown of TiO2 nanowires by chemical vapor deposition (CVD) on Ti/glass template. From the scanning electron microscope (SEM) it indicated the average length and diameter of TiO2 nanowires are 300 nm and 50 nm, respectively. We reported the growth of TiO2 nanowires and the fabrication of a TiO2 nanowire ultraviolet (UV) photodetector (PD). It was found that the fabricated TiO2 nanowire PD which is visible-blind with a cutoff wavelength around 390 nm. Compared with conventional film-type TiO2 PDs, it was found that we could achieve a 10 times larger photocurrent from the TiO2 nanowire PD. With an incident light wavelength of 390 nm and an applied bias of 5 V, it was found that the measured sensitivity were 6.85×10−2 and 7.65×10−3 mA/W for the TiO2 nanowire PD and the conventional film-type TiO2 PD, respectively. Furthermore, it was found that UV-to-visible rejection ratio observed from the TiO2 nanowire PD was also larger, as compared to conventional film-type TiO2 PDs. These results could be attributed to the nanowire have large surface area-to-volume ratio and absorb extra light more than conventional thin film. Based on the aforementioned, we also fabricate the TiO2 nanowires with polyvinylpyrrolidone (PVP) as an insulator layer for metal-insulator- semiconductor (MIS) PD application. Compared with a TiO2 nanowire metal-semiconductor-metal (MSM) PD, with a 5 V applied bias, it was found that dark currents measured from the TiO2 nanowire MIS PD and the TiO2 nanowire MSM PD were 4.95×10−10 and 9.52×10−10 A, respectively. It should attribute to the effective suppression of the leakage current by the PVP layer. Under the same 5 V applied bias, it was also found that photocurrents measured from the TiO2 nanowire MIS PD and the TiO2 nanowire MSM PD were 8.81×10−8 and 3.02×10−9 A, respectively. This should be attributed to the electron trappings related to the hydroxyl groups in PVP. With an incident light wavelength of 390 nm and an applied bias of 5 V, it was found that measured sensitivity were 2.46×10−3 and 7.08×10−5 A/W for the TiO2 nanowire MIS PD and the TiO2 nanowire MSM PD, respectively. In addition, the noise equivalent power (NEP) and the normalized detectivity (D*) of the fabricated TiO2 nanowire MIS PD and TiO2 nanowire MSM PD were 7.49×10−12 and 1.34×10−9 W, 8.86×1011 and 4.97×109 cm•Hz0.5•W−1, respectively. These results could be contribution the TiO2 nanowire UV PD have good practicality. Furthermore, we reported the deposition of p-Cu2O film onto n-TiO2 nanowires by DC magnetron sputtering and the fabrication of radial p-Cu2O-shell/n-TiO2-nanowire-core photodiodes. The p-Cu2O/n-TiO2 nanowire heterostructure exhibits rectifying behavior with a sharp turn on at 0.9 V. With a +10 V applied bias, the dark reverse leakage current of the diode was only around 3.37×10−8 A. However, the reverse leakage current increased rapidly to 1.15×10−6 A upon UV illumination.
On the part of TiO2 nanowire gas sensing, we reported the fabrication of TiO2 nanowire for ethanol, methanol, isopropyl alcohol (IPA) and acetone gas sensors application. With an indicate detection temperature of 300 °C, an applied bias of 1 V and gas concentration of 100 ppm, it was found that measured responsivity were 85, 71, 53 and 45 % for ethanol, methanol, IPA and acetone gas sensing. We found that all the above-mentioned gas has a good response, especially alcohol has more excellent performance. At the same condition, by measuring the I-V characteristics of the samples in ethanol, we found that the currents were of 17, 27, 60, 93, 125 and 191 nA when concentration at 5, 10, 30, 50, 80 and 100 ppm, respectively. In order to enhance ethanol gas sensing, we fabricated a TiO2 nanowire ethanol gas sensor under UV light illumination. The measured incremental responsivity was 28, 30, 42, 51, 67 and 89 % when concentration of the injected ethanol was 5, 10, 30, 50, 80 and 100 ppm, respectively. Compared with pure TiO2 nanowires, we could achieve a 4 times larger sensors responsivity from the TiO2 nanowires under UV light illumination in 5 ppm ethanol gas ambience. These results could be contribution the TiO2 nanowire ethanol gas sensor with well and keen sensitivity and business valuable.
Lastly, according to previous background, we report the growth of CuO:Zn nanowires by thermal oxidation on a glass template in ambient air for field emission application. The Zn content in the CuO nanowires approximated 9.9 %. Field emitters use these CuO:Zn nanowires were also fabricated on the glass substrate and compared with nanowires composed of CuO alone. The threshold fields of the CuO:Zn nanowire and CuO nanowires field emitters can be significantly decreased from 8.3 to 4.1 V/μm and the work function can also be reduced from 4.5 to 1.54 eV by introducing Zn atoms into the CuO nanowires. Furthermore, we report the adsorption of Au nanoparticles onto the surface of GaN nanowires through photo-enhanced chemical reaction and the fabrication of GaN nanowire field emitters. With the adsorption of Au nanoparticles, it was found that threshold field and work function were reduced from 8.29 V/μm and 4.1 eV to 6.67 V/μm and 3.2 eV, respectively. These improvements could be attributed to the larger band distortion and more electrons accumulation so that more electrons could be emitted for the GaN nanowire field emitters with Au nanoparticles.

Reference in chapter 1
[1] R. C. Weast and S. M. Selby, “Hand Book chemistry and physics,” CRC, 3rd edition, pp. 1245, 1967.
[2] P. A. Cox, “Transition Metal Oxides And Introduction to their electronic structure and properties,” Clarendon Press, Oxford, pp. 456, 1995.
[3] M. Walczak, E. L. Papadopoulou, M. Sanz, A. Manousaki, J. F. Marco, and M. Castillejo, “Structural and morphological characterization of TiO2 nanostructured films grown by nanosecond pulsed laser deposition,” Appl. Surf. Sci., vol. 255, pp. 5267-5270, 2010.
[4] N. Okubo, T. Nakazawa, Y. Katano, and I. Yoshizawa, “Fabrication of nanoparticles of anatase TiO2 by oxygen-supplied pulsed laser deposition,” Appl. Surf. Sci., vol. 197-198, pp. 679-683, 2002.
[5] http://ruby.colorado.edu/~smyth/min/tio2.html
[6] H. Lina, Abdul K. Rumaizb, Meghan Schulzc, Demin Wanga, Reza Rockd, C. P. Huanga, and S. Ismat Shah, “Photocatalytic activity of pulsed laser deposited TiO2 thin films,” Mater. Sci. Eng. B, vol. 151, pp. 133-139, 2008.
[7] M.O. Abou-Helal and W. T Seeber,. “Preparation of TiO2 thin films by spray pyrolysis to be used as a photocatalyst,” Appl. Surf. Sci., vol. 195, pp. 53-62, 2002.
[8] I. Hotovy, V. Rehacek. P. Siciliano, S. Capone, and L. Spiess, “Sensing characteristics of NiO thin films as NO2 gas sensor,” Thin Solid Films, vol. 418, pp. 9-15, 2002.
[9] S. Pokhrel, C. E. Simion, V. Quemener, N. Barsan, and U. Weimar, “Investigations of conduction mechanism in Cr2O3 gas sensing thick films by ac impedance spectroscopy and work function changes measurements,” Sens. Actuators B, vol. 133, pp. 78-83, 2008.
[10] W. Y. Li, L. N. Xu, and J. Chen, “Co3O4 nanomaterials in lithium-ion batteries and gas sensors,” Adv. Funct. Mater., vol. 15, pp. 851-857, 2005.
[11] L. Zhang, Q. Zhou, Z. Liu, X. Hou, Y. Li, and Y. Lv, “Novel Mn3O4 micro-octahedra: promising cataluminescence sensing material for acetone,” Chem. Mater., vol. 21, pp. 5066-5071, 2009.
[12] P. M. Jones, J. A. May, J. B. Reitz, and E. I. Solomon, “Electron spectroscopic studies of CH3OH chemisorption on Cu2O and ZnO single-crystal surfaces: Methoxide bonding and reactivity related to methanol synthesis,” J. Am. Chem. Soc., vol. 120, pp. 1506-1516, 1998.
[13] A. E. Rakhshani, “Preparation, characteristics and photovoltaic properties of cuprous-oxide-A-review,” Solid-State Electron., vol. 29, pp. 7-17, 1986.
[14] B. Balamurugan and B. R. Mehta, “Optical and structural properties of nanocrystalline copper oxide thin films prepared by activated reactive evaporation,” Thin Solid Films, vol. 396, pp. 90-96, 2001.
[15] A. H. MacDonald, “Superconductivity-copper oxide get charged up,” Nature, vol. 414, pp. 409-410, 2001.
[16] Y. P. Sukhorukov, N. N. Loshkareva, A. A. Samokhvalov, S. V. Naumov, A. S. Moskvin, and A. S. Ovchinnikov, “Magnetic phase transitions in optical spectrum of magnetic semiconductor CuO,” J. Magn. Magn. Mater., vol. 183, pp. 356-358, 1998.
[17] J. B. Reitz and E. I. Solomon, “Propylene oxidation on copper oxide surfaces: Electronic and geometric contributions to reactivity and selectivity,” J. Am. Chem. Soc., vol. 120, pp. 11467-11478, 1998.
[18] P. Poizot, S. Laruelle, S. Grugeon, L. Dupont, and J. M. Tarascon, “Nano-sized transition-metaloxides as negative-electrode materials for lithium-ion batteries,” Nature, vol. 407, pp. 496-499, 2000.
[19] J. Ghijsen, L. H. Tjeng, J. Vanelp, H. Eskes, J. Westerink, G. A. Sawatzky, and M. T. Czyzyk, “Electronic-structure of Cu2O and CuO,” Phys. Rev. B, vol. 38, pp. 11322-11330, 1988.
[20] C. T. Hsieh, J. M. Chen, H. H. Lin, and H. C. Shih, “Field emission from various CuO nanostructures,” Appl. Phys. Lett., vol. 83, pp. 3383-3385, 2003.
[21] Y. W. Zhu, T. Yu, F. C. Cheong, X. J. Xu, C. T. Lim, V. B. C. Tan, J. T. L. Thong, and C. H. Sow, “Large-scale synthesis and field emission properties of vertically oriented CuO nanowire films,” Nanotechnology, vol. 16, pp. 88-92, 2005.
[22] J. Wu, W. Walukiewicz, K. M. Yu, J. W. Ager, E. E. Haller, H. Lu, and William J. Schaff, “Small band gap bowing in In1-xGaxN alloys,“ Appl. Phys. Lett., vol. 80, pp. 4741-4743, 2002.
[23] http://www.nano.gov/nanotech-101/what/nano-size
[24] S. Iijima, “Helical microtubules of graphitic carbon,” Nature, vol. 354, pp. 56-58, 1991.
[25] J. M. Bao, M. A. Zimmler, F. Capasso, X. W. Wang, and Z. F. Ren, “Broadband ZnO single-nanowire light-emitting diode,” Nano Lett., vol. 6, pp. 1719-1722, 2006.
[26] Y. F. Lin and W. B. Jian, “The impact of nanocontact on nanowire based nanoelectronics,” Nano Lett., vol. 8, pp. 3146-3150, 2008.
[27] M. H. Huang, S. Mao, H. Feick, H. Q. Yan, Y. Y. Wu, H. Kind, E. Weber, R. Russo, and P. D. Yang, “Room-temperature ultraviolet nanowire nanolasers,” Science, vol. 292, pp. 1897-1899, 2001.
[28] H. Kind, H. Q. Yan, B. Messer, M. Law, and P. D. Yang, “Nanowire ultraviolet photodetectors and optical switches,” Adv. Mater., vol. 14, pp. 158-160, 2002.
[29] L. Gangloff, E. Minoux, K. B. K. Teo, P. Vincent, V. T. Semet, V. T. Binh, M. H. Yang, I. Y. Y. Bu, R. G. Lacerda, G. Pirio, J. P. Schnell, D. Pribat, D. G. Hasko, G. A. J. Amaratunga, W. I. Milne, and P. Legagneux, “Self-aligned, gated arrays of individual nanotube and nanowire Emitters,” Nano Lett., vol. 4, pp. 1575-1579, 2004.
[30] F. S. Baker, J. Williams, and A. R. Osborn, “Field emission from carbon fibres: A new electron source,” Nature, vol. 239, pp. 96-97, 1972.
[31] C. J. Lee, T. J. Lee, S. C. Lyu, Y. Zhang, H. Ruh, and H. J. Lee, “Field emission from well-aligned zinc oxide nanowires grown at low temperature,” Appl. Phys. Lett., vol. 81, pp. 3648-3650, 2002.
[32] H. B. Jia, Y. Zhang, X. H. Chen, J. Shu, X. H. Luo, Z. S. Zhang, and D. P. Yu, “Efficient field emission from single crystalline indium oxide pyramids,” Appl. Phys. Lett., vol. 82, pp. 4146-4148, 2003.
[33] J. Zhou, S. Z. Deng, N. S. Xu, J. Chen, and J. C. She, “Synthesis and field-emission properties of aligned MoO3 nanowires,” Appl. Phys. Lett., vol. 83, pp. 2653-2655, 2003.
[34] Y. J. Chen, Q. H. Li, Y. X. Liang, T. H. Wang, Q. Zhao, and D. P. Yu, “Field-emission from long SnO2 nanobelt arrays,” Appl. Phys. Lett., vol. 85, pp. 5682-5684, 2004.
[35] K. K. Manga, S. Wang, M. Jaiswal, Q. Bao, and K. P. Loh, “High-Gain Graphene-Titanium Oxide Photoconductor Made from Inkjet Printable Ionic Solution,” Adv. Mater., vol. 22, pp. 5265-5270, 2010.
[36] J. Zhang, C. Cai, F. Pan, W. Hao, W. Zhang, and T. Wang, “Employment of a metal microgrid as a front electrode in a sandwich-structured photodetector,” Appl. Optic., vol. 48, pp. 3638-3642, 2009.
[37] Y. Han, G. Wu, H. Li, M. Wang, and H. Chen, “Highly efficient ultraviolet photodetectors based on TiO2 nanocrystal-polymer composites via wet processing,” Nanotechnology, vol. 21, p. 185708, 2010.
[38] H. Xue, X. Kong, Z. Liu, C. Liu, J. Zhou, and W. Chen, “TiO2 based metal-semiconductor-metal ultraviolet photodetectors,” Appl. Phys. Lett., vol. 90, pp. 201118-201120, 2007.
[39] J. Xing, H. Wei, E. J. Guo, and F. Yang, “Highly sensitive fast-response UV photodetectors based on epitaxial TiO2 films,” J. Phys. D: Appl. Phys., vol. 44, pp. 375104-375108, 2011.
[40] S. Panigrahi and D. Basak, “Core-shell TiO2@ZnO nanorods for efficient ultraviolet photodetection,” Nanoscale, vol. 3, pp. 2336-2341, 2011.
[41] J. Zou, Q. Zhang, K. Huang, and N. Marzari, “Ultraviolet Photodetectors Based on Anodic TiO2 Nanotube Arrays,“ J. Phys. Chem. C, vol. 114, pp. 10725-10729, 2010.
[42] A, Kolmakov, Y. X. Zhang, G. S. Cheng, M. Moskovits, “Detection of CO and O2 Using Tin Oxide Nanowire Sensors,” Adv. Mater., vol. 15, pp. 997-1000, 2003.
[43] B. Timmer, W. V. D. Olthuis, A. Berg, “Ammonia sensors and their applications-a review,” Sens. Actuators B, vol. 107, pp. 666-677, 2005.

Reference in chapter 2
[1] Whisker Technology (Ed: A. P. Levitt), Wiley-Interscience, New York, 1970.
[2] M. Volmer, I. Estermann, “Über den Mechanismus der Molekülabscheidung an Kristallen,” Z. Phys. A, vol. 7, pp. 13-17, 1921.
[3] G. W. Sears, “Mercury Whiskers,” Acta Metall., vol. 1, pp. 457-459, 1953.
[4] Z. W. Pan, Z. R. Dai, and Z. L. Wang, “Nanobelts of semiconducting oxides,” Science, vol. 291, pp. 1947-1948, 2001.
[5] H. Zhang, A. C. Dohnalkova, C. Wang, J. S. Young, E. C. Buck, and L. Wang, “Lithium-assisted self-assembly of aluminum carbide nanowires and nanoribbons,” Nano Lett., vol. 2, pp. 105-108, 2002.
[6] X. Jiang, T. Herricks, and Y. Xia, “CuO nanowires can be synthesized by heating copper substrates in air,” Nano Lett., vol. 2, pp. 1333-1338, 2002.
[7] Y. Xia, P. Yang, Y. Sun, Y. Wu, B. Mayers, B. Gates, Y. Yin, F. Kim, and H. Yan, “One-dimensional nanostructures: Synthesis, characterization, and applications,” Adv. Mater., vol. 15, pp. 353-389, 2003.
[8] C. S. Rout, G. U. Kulkarni, and C. N. R. Rao, “Room temperature hydrogen and hydrocarbon sensors based on single nanowires of metal oxides,” J. Phys. D. Appl. Phys., vol. 40, pp. 2777-2782, 2007.
[9] P. Hu, G. Du, W. Zhou, J. Cui, J. Lin, H. Liu, D. Liu, J. Wang, and S. Chen, “Enhancement of ethanol vapor sensing of TiO2 nanobelts by surface engineering,” J. Am. Chem. Soc., vol. 2, pp. 3263-3269, 2010.
[10] O. Landau, A. Rothschild, and E. Zussman, “Processing microstructure properties correlation of ultrasensitive gas sensors produced by electrospinning,” Chem. Mater., vol. 21, pp. 9-11, 2009.
[11] W. Biao, Z. Y. Dong, H. L. Ming, C. J. Sheng, G. F. Li, L. Yun, and W. L. Jun, “Improved and excellent CO sensing properties of Cu-doped TiO2 nanofibers,” Chin. Sci. Bull., vol. 55, pp. 228-232, 2010.
[12] O. K. Varghese, D. Gong, M. Paulose, K. G. Ong, and C. A. Grimes, “Hydrogen sensing using titania nanotubes,” Sens. Actuators B Chem., vol. 93, pp. 338-344, 2003.
[13] A. Hu, C. Cheng, X. Li, J. Jiang, R. Ding, J. Zhu, F. Wu, J. Liu, and X. Huang, “Two novel hierarchical homogeneous nanoarchitectures of TiO2 nanorods branched and P25-coated TiO2 nanotube arrays and their photocurrent performances,” Nanoscale. Res. Lett., vol. 6, pp. 2-6, 2011.
[14] S. Yoo, S. A. Akbar, and K. H. Sandhage, “Nanocarving of titania (TiO2): A novel approach for fabricating chemical sensing platform,” Ceram. Int., vol. 30, pp. 1121-1126, 2004.
[15] C. M. Carney, S. Yoo, and S. A. Akbar, “TiO2-SnO2 nanostructures and their H2 sensing behavior,” Sens. Actuators B Chem., vol. 108, pp. 29-33, 2005.
[16] L. Francioso, A. M. Taurino, A. Forleo, and P. Siciliano, “TiO2 nanowires array fabrication and gas sensing properties,” Sens. Actuators B Chem., vol. 130, pp. 70-76, 2008.
[17] M. M. Arafat, B. Dinan, S. A. Akbar, and A. S. M. A. Haseeb, “Gas sensors based on one-dimensional nanostructured metal-oxides: A review,” Sensors, vol. 12, pp. 7207-7258, 2012.
[18] S. Iijima, “Helical microtubules of graphitic carbon,” Nature, vol. 354, pp. 56-58, 1991.
[19] A. G. Rinzler, J. H. Hafner, P. Nikolaev, L. Lou, S. G. Kim, D. Tomanek, P. Nordlander, D. T. Colbert, and R. E. Smalley, “Unraveling nanotubes: field emission from an atomic wire,” Science, vol. 269, pp. 1550-1553, 1995.
[20] L. A. Chernozatonskii, Y. V. Gulyaev, Z. J. Kosakovskaja, N. I. Sinitsyn, G. V. Torgashov, Y. F. Zakharchenko, E. A. Fedorov, and V. P. Val'chuk, “Electron field emission from nanofilament carbon films,” Chem. Phys. Lett., vol. 233, pp. 63-68, 1995.
[21] W. A. Deheer, A. Chatelain, and D. Ugarte, “A carbon nanotube field-emission electron source,” Science, vol. 270, pp. 1179-1180, 1995.
[22] R. H. Fowler and L. Nordheim, “Electron emission in intense electric fields,” Proc. R. Soc., vol. 119, pp. 173-181, 1928.
[23] Y. W. Zhu, T. Yu, F. C. Cheong, X. J. Xu, and C. H. Sow, “Largescale synthesis and field emission properties of vertically oriented CuO nanowire films,” Nanotechnology, vol. 16, pp. 88-92, 2005.
[24] V. Filip, D. Nicolaescu, M. Tanemura, and F. Okuyama, “Modeling the electron field emission from carbon nanotube films,” Ultramicroscopy, vol. 89, pp. 39-49, 2001.
[25] G. P. Beukcma, “Conditioning of a vacuum gap by sparks and ion bombardmemt,” Physica, vol. 61, pp. 259-274, 1971.
[26] R. E. Burgess and H. Kroemer, “Corrected values of Fowler-Nordheim field emission functions v(y) and s(y),” Phys. Rev. A, vol. 90, p. 515, 1953.
[27] C. Lea, “Field emission from tetrahedral amorphous carbon,” Appl. Phys. Lett., vol. 71, pp. 1430-1432, 1997.
[28] P. Mitra, A. P. Chatterjee, and H. S. Maiti, “ZnO thin film sensor”, Mater. Lett., vol. 35, pp. 33-38, 1998.
[29] Q. Wan, Q. H. Li, Y. J. Chen, T. H. Wang, X. L. He, J. P. Li, and C. L. Lin, “Fabrication and ethanol sensing characteristics of ZnO nanowire gas sensors”, Appl. Phys. Lett., vol. 84, pp. 3654-3656, 2004.
[30] M. Batzill and U. Diebold, “Surface studies of gas sensing metal oxides”, Phys. Chem. Chem. Phys., vol. 9, pp. 2307-2318, 2007.
[31] J. Cerd`a Belmonte, J. Manzano, J. Arbiol, A. Cirera, J. Puigcorb´e, A. Vil`a, N. Sabat´e, I. Gr`acia, C. Can´e, and J. R. Morante, “Micromachined twin gas sensor for CO and O2 quantification based on catalytically modified nano-SnO2”, Sens. Actuators B, vol. 114, pp. 881-892, 2006.
[32] P. P. Sahay, “Zinc oxide thin film gas sensor for detection of acetone”, J. Mater. Sci., vol. 40, pp. 4383-4385, 2005.
[33] Y. Wang, J. Chen, and X. Wu, “Preparption and gas-sensing properites of perovskite-type SrFeO3 oxide”, Mater. Lett., vol. 49, pp. 361-364, 2001.
[34] A. Kolmakov, Y. Zhang, G. Chen, and M. Moskovits, “Detection of CO and O2 using tin oxide nanowire sensor”, Adv. Mater., vol. 12, pp. 997-1000, 2003.

Reference in chapter 3
[1] Z. Yu and M. Aceves-Mijares, “A ultraviolet-visible-near infrared photodetector using nanocrystalline Si superlattice,” Appl. Phys. Lett., vol. 95, p. 081101, 2009.
[2] H. Huang, Y. Xie, W. Yang, F. Zhang, J. Cai, and Z. Wu, “Low-Dark-Current TiO2 MSM UV Photodetectors With Pt Schottky Contacts,” IEEE Electron. Dev. Lett., vol. 32, pp. 530-532, 2011.
[3] H. Xue, X. Kong, Z. Liu, C. Liu, J. Zhou, W. Chen, S. Ruan, and Q. Xu, “TiO2 based metal-semiconductor-metal ultraviolet photodetectors,” Appl. Phys. Lett., vol. 90, p. 201118, 2007.
[4] D. S. Dhawale, R. R. Salunkhe, U. M. Patil, K. V. Gurav, A. M. More, and C. D. Lokhande, “Room temperature liquefied petroleum gas (LPG) sensor based on p-polyaniline/n-TiO2 heterojunction,” Sens. Actuators B, vol. 134, pp. 988-992, 2008.
[5] L. Casta˜neda, A. Maldonado, and M. de la L. Olvera, “Sensing properties of chemically sprayed TiO2 thin films using Ni, Ir, and Rh as catalysts,” Sens. Actuators B, vol. 133, pp. 687-693, 2008.
[6] Y. Li, Y. Jiang, S. Peng, and F. Jiang, “Nitrogen-doped TiO2 modified with NH4F for efficient photocatalytic degradation of formaldehyde under blue light-emitting diodes,” J. Hazard. Mater., vol. 182, pp. 90-96, 2010.
[7] X. Wang and T. T. Lim, “Solvothermal synthesis of C-N codoped TiO2 and photocatalytic evaluation for bisphenol A degradation using a visible-light irradiated LED photoreactor,” Appl. Catal. B-Environ., vol. 100, pp. 355-364, 2010.
[8] Y. Chiba, A. Islam, R. Komiya, N. Koide, and L. Han, “Conversion efficiency of 10.8% by a dye-sensitized solar cell using a TiO2 electrode with high haze,” Appl. Phys. Lett., vol. 88, p. 223505, 2006.
[9] N. Kopidakis, N. R. Neale, K. Zhu, J. van de Lagemaat, and A. J. Frankb, “Spatial location of transport-limiting traps in TiO2 nanoparticle films in dye-sensitized solar cells,” Appl. Phys. Lett., vol. 87, p. 202106, 2005.
[10] L. Shen, G. Zhu,W. Guo, C. Tao, X. Zhang, C. Liu,W. Chen, S. Ruan, and Z. Zhong, “Performance improvement of TiO2/P3HT solar cells using CuPc as a sensitizer,” Appl. Phys. Lett., vol. 92, p. 073307, 2008.
[11] W. Y. Weng, T. J. Hsueh, S. J. Chang, S. B. Wang, H. T. Hsueh, and G. J. Huang, “A High-Responsivity GaN Nanowire UV Photodetector,” IEEE J. Sel. Top. Quant. Electron., vol. 17, pp. 996-1001, 2011.
[12] W. Y. Weng, S. J. Chang, C. L. Hsu, and T. J. Hsueh, “A ZnO-nanowire phototransistor prepared on glass substrates,” ACS Appl. Mater. Interfaces, vol. 3, pp. 162-166, 2011.
[13] J. M. Wu, H. C. Shih, and W. T. Wu, “Electron field emission from single crystalline TiO2 nanowires prepared by thermal evaporation,” Chem. Phys. Lett., vol. 413, pp. 490-494, 2005.
[14] J. M. Wu, H. C. Shih, and W. T. Wu, “Formation and photoluminescence of single-crystalline rutile TiO2 nanowires synthesized by thermal evaporation,” Nanotechnology, vol. 17, pp. 105-109, 2006.
[15] Y. W. Heo, B. S. Kang, L. C. Tien, D. P. Norton, F. Ren, J. R. La Roche, and S. J. Pearton, “UV photoresponse of single ZnO nanowires,” Appl. Phys. A, vol. 80, pp. 497-499, 2005.
[16] J. A. Garrido, E. Monroy, I. Izpura, and E. Munoz, “Photoconductive gain modelling of GaN photodetectors,” Semicond. Sci. Technol., vol. 13, pp. 563-568, 1998.
[17] C. Soci, A. Zhang, B. Xiang, S. A. Dayeh, D. P. R. Aplin, J. Park, X. Y. Bao, Y. H. Lo, and D. Wang, “ZnO nanowire UV photodetectors with high internal gain,” Nano Lett., vol. 7, pp. 1003-1009, 2007.
[18] C. H. Lin, R. S. Chen, T. T. Chen, H. Y. Chen, Y. F. Chen, K. H. Chen, and L. C. Chen, “High photocurrent gain in SnO2 nanowires,” Appl. Phys. Lett., vol. 93, p. 112115, 2008.
[19] L. W. Ji, S. M. Peng, Y. K. Su, S. J. Young, C. Z. Wu, and W. B. Cheng, “Ultraviolet photodetectors based on selectively grown ZnO nanorod arrays,” Appl. Phys. Lett., vol. 94, p. 203106, 2009.
[20] S. B. Kim, H. T. Huang, and S. C. Hong, “Photocatalytic degradation of volatile organic compounds at the gas-solid interface of a TiO2 photocatalyst,” Chemosphere, vol. 48, pp. 437-444, 2002.
[21] G. K. Mor, K. Shankar, M. Paulose, O. K. Varghese, and C. A. Grimes, “Use of highly-ordered TiO2 nanotube arrays in dye-sensitized solar cells,” Nano Lett., vol. 6, pp. 215-218, 2006.
[22] C. Garzella, E. Comini, E. Tempesti, C. Frigeri, and G. Sberveglieri, “TiO2 thin films by a novel sol-gel processing for gas sensor applications,” Sens. Actuators B, vol. 68, pp. 189-196, 2000.
[23] H. Xue, X. Kong, Z. Liu, C. Liu, J. Zhou, W. Chen, S. Ruan, and Q. Xu, “TiO2 based metal-semiconductor-metal ultraviolet photodetectors,” Appl. Phys. Lett., vol. 90, p. 201118, 2007.
[24] H. Huang,W. Yang, Y. Xie, X. Chen, and Z.Wu, “Metal-semiconductor-metal ultraviolet photodetectors based on TiO2 films deposited by radio frequency magnetron sputtering,” IEEE Electron. Dev. Lett., vol. 31, pp. 588-590, 2010.
[25] W. S. Shih, S. J. Young, L. W. Ji, W. Water, T. H. Meen, and H. W. Shiu, “Effect of oxygen plasma treatment on characteristics of TiO2 photodetectors,” IEEE Sens. J., vol. 11, pp. 2031-2045, 2011.
[26] C. Soci, A. Zhang, B. Xiang, S. A. Dayeh, D. P. R. Aplin, J. Park, X. Y. Bao, Y. H. Lo, and D. Wang, “ZnO nanowire UV photodetectors with high internal gain,” Nano Lett., vol. 7, pp. 1003-1009, 2007.
[27] R. S. Chen, C. A. Chen, H. Y. Tsai,W. C.Wang, and Y. S. Huang, “Photoconduction properties in single-crystalline titanium dioxide nanorods with ultrahigh normalized gain,” J. Phys. Chem. C, vol. 116, pp. 4267-4272, 2012.
[28] T. Y. Tsai, S. J. Chang, W. Y. Weng, C. L. Hsu, S. H. Wang, C. J. Chiu, and T. J. Hsueh, “A visible-blind TiO2 nanowire photodetector,” J. Electrochem. Soc., vol. 159, pp. J132-J135, 2012.
[29] H. Klauk, M. Halik, U. Zschieschang, G. Schmid, and W. Radlik, “Highmobility polymer gate dielectric pentacene thin film transistors,” J. Appl. Phys., vol. 92, pp. 5259-5263, 2002.
[30] S. Lee, B. Koo, J. Shin, E. Lee, H. Park, and H. Kim, “Effects of hydroxyl groups in polymeric dielectrics on organic transistor performance,” Appl. Phys. Lett., vol. 88, p. 162109, 2006.
[31] Y. W. Heo, B. S. Kang, L. C. Tien, D. P. Norton, F. Ren, J. R. LaRoche, and S. J. Pearton, “UV photoresponse of single ZnO nanowires,” Appl. Phys. A, vol. 80, pp. 497-499, 2005.
[32] S. J. Chang, K. H. Lee, P. C. Chang, Y. C. Wang, C. L. Yu, C. H. Kuo, and S. L. Wu, “GaN-based Schottky barrier photodetectors with a 12-pair MgxNy-GaN buffer layer,” IEEE J. Quan. Electron., vol. 44, pp. 916-921, 2008.
[33] Y. Z. Chiou, Y. K. Su, S. J. Chang, J. Gong, Y. C. Lin, S. H. Liu, and C. S. Chang, “High detectivity InGaN-GaN multiquantum well p-n junction photodiodes,” IEEE J. Quan. Electron., vol. 39, pp. 681-685, 2003.
[34] E. Monroy, F. Calle, E. Munoz, F. Omnes, B. Beaumont, and P. Gibart, “Visible-blindness in photoconductive and photovoltaic AlGaN ultraviolet detectors,” J. Electron. Mater., vol. 28, pp. 240-245, 1999.
[35] S. J. Chang, T. K. Ko, Y. K. Su, Y. Z. Chiou, C. S. Chang, S. C. Shei, J. K. Sheu, W. C. Lai, Y. C. Lin, W. S. Chen, and C. F. Shen, “GaN-based p-i-n sensors with ITO contacts,” IEEE Sens. J., vol. 6, pp. 406-411, 2006.
[36] J. Zhang, H. Zhao, and N. Tansu, “Large optical gain AlGaN-delta-GaN quantum wells laser active regions in mid- and deep-ultraviolet spectral regimes,” Appl. Phys. Lett., vol. 98, p. 171111, 2011.
[37] J. Zhang, H. Tong, G. Liu, J. A. Herbsommer, G. Huang, and N. Tansu, “Characterizations of Seebeck coefficients and thermoelectric figures of merit for AlInN alloys with various In-contents,” J. Appl. Phys., vol. 109, p. 053706, 2011.
[38] J. Zhang, S. Kutlu, G. Liu, and N. Tansu, “High-temperature characteristics of Seebeck coefficients for AlInN alloys grown by metalorganic vapor phase epitaxy,” J. Appl. Phys., vol. 110, p. 043710, 2011.
[39] W. Y. Weng, S. J. Chang, C. L. Hsu, and T. J. Hsueh, “A ZnO nanowire phototransistor prepared on glass substrates,” ACS Appl. Mater. Interfaces, vol. 3, pp. 162-166, 2011.
[40] T. K. Lin, S. J. Chang, Y. K. Su, Y. Z. Chiou, C. K. Wang, C. M. Chang, and B. R. Huang, “ZnSe homoepitaxial MSM photodetectors with transparent ITO contact electrodes,” IEEE Trans. Electron. Dev., vol. 52, pp. 121-123, 2005.
[41] Y. Chiba, A. Islam, R. Komiya, N. Koide, and L. Han, “Conversion efficiency of 10.8% by a dye-sensitized solar cell using a TiO2 electrode with high haze,” Appl. Phys Lett., vol. 88, p. 223505, 2006.
[42] N. Kopidakis, N. R. Neale, K. Zhu, J. V. D. Lagemaat, and A. J. Frank, “Spatial location of transport-limiting traps in TiO2 nanoparticle films in dye-sensitized solar cells,” Appl. Phys. Lett., vol. 87, p. 202106, 2005.
[43] L. Shen, G. Zhu, W. Guo, C. Tao, X. Zhang, C. Liu, W. Chen, S. Ruan, and Z. Zhong, “Performance improvement of TiO2/P3HT solar cells using CuPc as a sensitizer,” Appl. Phys. Lett., vol. 92, p. 073307, 2008.
[44] H. Xue, X. Kong, Z. Liu, C. Liu, J. Zhou, W. Chen, S. Ruan, and Q, Xu, “TiO2 based metal-semiconductor-metal ultraviolet photodetectors,” Appl. Phys. Lett., vol. 90, p. 201118, 2007.
[45] X. Kong, C. Liu, W. Dong, X. Zhang, C. Tao, L. Shen, J. Zhou, Y. Fei, and S. Ruan, “Metal-semiconductor-metal TiO2 ultraviolet detectors with Ni electrodes,” Appl. Phys. Lett., vol. 94, p. 123502, 2009.
[46] K. J. Zhang, W. Xu, X. J. Li, S. J. Zheng, G. Xu, and J. H. Wang, “Photocatalytic oxidation activity of titanium dioxide film enhanced by Mn non-uniform doping,” Trans. Nonferrous Met. Soc. China, vol. 16, pp. 1069-1075, 2006.
[47] J. P. Yasomanee and J. Bandara, “Multi-electron storage of photoenergy using Cu2O-TiO2 thin film photocatalyst,” Sol. Energ. Mat. Sol. Cells., vol. 92, pp. 348-352, 2008.
[48] Y. G. Zhang, L. L. Ma, J. L. Li, and Y. Yu, “In situ Fenton reagent generated from TiO2/Cu2O composite film: a new way to utilize TiO2 under visible light irradiation,” Environ. Sci. Technol., vol. 41, pp. 6264-6269, 2007.
[49] W. Siripala, A. Ivanovskaya, T. F. Jaramillo, S. H. Baeck, and E. W. McFarland, “A Cu2O/TiO2 heterojunction thin film cathode for photoelectrocatalysis,” Sol. Energ. Mat. Sol. Cells., vol. 77, pp. 229-237, 2003.
[50] J. Ghijsen, L. H. Tjeng, J. V. Elp, H. Eskes, J. Westerink, G. A. Sawatzky, and M. T. Czyzyk, “Electronic structure of Cu2O and CuO,” Phys. Rev. B, vol. 38, pp. 11322-11330, 1988.
[51] S. Ishizuka, S. Kato, Y. Okamoto, T. Sakurai, K. Akimoto, N. Fujiwara, and H. Kobayashi, “Passivation of defects in polycrystalline Cu2O thin films by hydrogen or cyanide treatment,” Appl. Surf. Sci., vol. 216, pp. 94-97, 2003.
[52] J. Herion, E. A. Niekisch, and G. Scharl, “Investigation of metal oxide/cuprous oxide heterojunction solar cells,” Sol. Energy. Mater., vol. 4, pp. 101-112, 1980.
[53] E. Fortin and D. Masson, “Photovoltaic effects in Cu2O-Cu solar cells grown by anodic oxidation,” Solid State Electron., vol. 25, pp. 281-283, 1982.
[54] C. A. N. Fernando and S. K. Wetthasinghe, “Investigation of photo- electrochemical characteristics of n-type Cu2O films,” Sol. Energ. Mat. Sol. Cells., vol. 63, pp. 299-308, 2000.
[55] L. Armelao, D. Barreca, M. Bertapelle, Y. Bottaro, C. Sada, and E. Tondello, “A sol-gel approach to nanophasic copper oxide thin films,” Thin Solid Films, vol. 442, pp. 48-52, 20003.
[56] T. D. Golden, M. G. Shumsky, Y. Zhou, R. A. VanderWerf, R. A. V. Leeuwen, and J. A. Switzer, “Electrochemical deposition of copper (I) oxide films,” Chem. Mater., vol. 8, pp. 2499-2504, 1996.
[57] T. Mahalingam, J. S. P. Chitra, J. P. Chu, and P. J. Sebastian, “Preparation and microstructural studies of electrodeposited Cu2O thin films,” Mater. Lett., vol. 58, pp. 1802-1807, 2004.
[58] T. J. Hsueh, H. Y. Chen, T. Y. Tsai, W. Y. Weng, Y. M. Yeh, B. T. Dai, and J. M. Shieh, “Si nanowire-based photovoltaic devices prepared at various temperatures,” IEEE Electron. Dev. Lett., vol. 31, pp. 1275-1277, 2010.
[59] J. M. Wu, H. C. Shih, and W. T. Wu, “Electron field emission from single crystalline TiO2 nanowires prepared by thermal evaporation,” Chem. Phys. Lett., vol. 413, pp. 490-494, 2005.
[60] J. M. Wu, H. C. Shih, and W. T. Wu, “Formation and photoluminescence of single crystalline rutile TiO2 nanowires synthesized by thermal evaporation,” Nanotechnology, vol. 17, pp. 105-109, 2006.

Reference in chapter 4
[1] D. S. Dhawale, R. R. Salunkhe, U. M. Patil, K. V. Gurav, A. M. More, and C. D. Lokhande, “Room temperature liquefied petroleum gas (LPG) sensor based on p-polyaniline/n-TiO2 heterojunction,” Sens. Actuators B, vol. 134, pp. 988-992, 2008.
[2] L. Castaneda, A. Maldonado, and M. de la L. Olvera, “Sensing properties of chemically sprayed TiO2 thin films using Ni, Ir, and Rh as catalysts,” Sens. Actuators B, vol. 133, pp. 687-693, 2008.
[3] Y. Li, Y. Jiang, S. Peng, and F. Jiang, “Nitrogen-doped TiO2 modified with NH4F for efficient photocatalytic degradation of formaldehyde under blue light-emitting diodes,” J. Hazard. Mater., vol. 182, pp. 90-96, 2010.
[4] X. Wang and T. T. Lim, “Solvothermal synthesis of C-N codoped TiO2 and photocatalytic evaluation for bisphenol A degradation using a visible-light irradiated LED photoreactor,” Appl. Catal. B-Environ., vol. 100, pp. 355-364, 2010.
[5] Y. Chiba, A. Islam, R. Komiya, N. Koide, and L. Han, “Conversion efficiency of 10.8% by a dye-sensitized solar cell using a TiO2 electrode with high haze,” Appl. Phys. Lett., vol. 88, p. 223505, 2006.
[6] N. Kopidakis, N. R. Neale, K. Zhu, J. van de Lagemaat, and A. J. Frankb, “Spatial location of transport-limiting traps in TiO2 nanoparticle films in dye-sensitized solar cells,” Appl. Phys. Lett., vol. 87, p. 202106, 2005.
[7] L. Shen, G. Zhu,W. Guo, C. Tao, X. Zhang, C. Liu,W. Chen, S. Ruan, and Z. Zhong, “Performance improvement of TiO2/P3HT solar cells using CuPc as a sensitizer,” Appl. Phys. Lett., vol. 92, p. 073307, 2008.
[8] R. Rella, J. Spadavecchia, M. G. Manera, S. Capone, A. Taurino, M. Martino, A. P. Caricato, and T. Tunno, “Acetone and ethanol solid-state gas sensors based on TiO2 nanoparticles thin film deposited by matrix assisted pulsed laser evaporation,” Sens. Actuators B, vol. 127, pp. 426-431, 2007.
[9] M. G. Manera, J. Spadavecchia, D. Buso, C. de Julian Fernandez, G. Mattei, A. Martucci, P. Mulvaney, J. Perez-Juste, R. Rella, L. Vasanelli, and P. Mazzoldi, “Optical gas sensing of TiO2 and TiO2/Au nanocomposite thin films,” Sens. Actuators B, vol. 132, pp. 107-115, 2008.
[10] H. F. Lu, F. Li, G. Liu, Z. G. Chen, D. W. Wang, H. T. Fang, G. Q. Lu, Z. H. Jiang, and H. M. Cheng, “Amorphous TiO2 nanotube arrays for low-temperature oxygen sensors,” Nanotechnology, vol. 19, pp. 405504-405511, 2008.
[11] H. Liu, D. Ding, C. Ning, and Z. Li, “Wide-range hydrogen sensing with Nb-doped TiO2 nanotubes,” Nanotechnology, vol. 23, pp. 015502-015507, 2012.
[12] V. Galstyan, E. Comini, G. Faglia, A. Vomiero, L. Borgese, E. Bontempi, and G. Sberveglieri, “Fabrication and investigation of gas sensing properties of Nb-doped TiO2 nanotubular arrays,” Nanotechnology, vol. 23, p. 235706, 2012.
[13] P. Hu, G. Du, W. Zhou, J. Cui, J. Lin, H. Liu, D. Liu, J. Wang, and S. Chen, “Enhancement of ethanol vapor sensing of TiO2 nanobelts by surface engineering,” ACS Appl. Mater. Interfaces, vol. 2, pp. 3263-3269, 2010.
[14] H. W. Lin, Y. H. Chang, and C. Chen, “Facile fabrication of TiO2 nanorod arrays for gas sensing using double-layered anodic oxidation method,” J. Electrochem. Soc., vol. 159, pp. K5-K9, 2012.
[15] M. Epifani, T. Andreu, R. Zamani, J. Arbiol, E. Comini, P. Siciliano, G. Faglia, and J. R. Moranteb, “Pt doping triggers growth of TiO2 nanorods: nanocomposite synthesis and gas-sensing properties,” CrystEngComm., vol. 14, pp. 3882-3887, 2012.
[16] L. Francioso, A. M. Taurino, A. Forleo, and P. Siciliano, “TiO2 nanowires array fabrication and gas sensing properties,” Sens. Actuators B, vol. 130, pp. 70-76, 2008.
[17] T. J. Hsueh, C. L. Hsu, S. J. Chang, and I. C. Chen, “Laterally grown ZnO nanowire ethanol gas sensors,” Sens. Actuators B, vol. 126, pp. 473-477, 2007.
[18] A. Kolmakov, Y. X. Zhang, G. S. Cheng, M. Moskovits, “Detection of CO and O2 Using Tin Oxide Nanowire Sensors,” Adv. Mater., vol. 15, pp. 997-1000, 2003.
[19] B. Timmer, W. V. D. Olthuis, A. Berg, “Ammonia sensors and their applications-a review,” Sens. Actuators B, vol. 107, pp. 666-677, 2005.
[20] D. S. Dhawale, R. R. Salunkhe, U. M. Patil, K. V. Gurav, A. M. More, and C. D. Lokhande, “Room temperature liquefied petroleum gas (LPG) sensor based on p-polyaniline/n-TiO2 heterojunction,” Sens. Actuators B, vol. 134, pp. 988-992, 2008.
[21] L. Castaneda, A. Maldonado, and M. de la L. Olvera, “Sensing properties of chemically sprayed TiO2 thin films using Ni, Ir, and Rh as catalysts,” Sens. Actuators B, vol. 133, pp. 687-693, 2008.
[22] Y. Li, Y. Jiang, S. Peng, and F. Jiang, “Nitrogen-doped TiO2 modified with NH4F for efficient photocatalytic degradation of formaldehyde under blue light-emitting diodes,” J. Hazard. Mater., vol. 182, pp. 90-96, 2010.
[23] X. Wang and T. T. Lim, “Solvothermal synthesis of C-N codoped TiO2 and photocatalytic evaluation for bisphenol A degradation using a visible-light irradiated LED photoreactor,” Appl. Catal. B-Environ., vol. 100, pp. 355-364, 2010.
[24] Y. Chiba, A. Islam, R. Komiya, N. Koide, and L. Han, “Conversion efficiency of 10.8% by a dye-sensitized solar cell using a TiO2 electrode with high haze,” Appl. Phys. Lett., vol. 88, p. 223505, 2006.
[25] N. Kopidakis, N. R. Neale, K. Zhu, J. van de Lagemaat, and A. J. Frankb, “Spatial location of transport-limiting traps in TiO2 nanoparticle films in dye-sensitized solar cells,” Appl. Phys. Lett., vol. 87, p. 202106, 2005.
[26] L. Shen, G. Zhu,W. Guo, C. Tao, X. Zhang, C. Liu,W. Chen, S. Ruan, and Z. Zhong, “Performance improvement of TiO2/P3HT solar cells using CuPc as a sensitizer,” Appl. Phys. Lett., vol. 92, p. 073307, 2008.
[27] R. Rella, J. Spadavecchia, M. G. Manera, S. Capone, A. Taurino, M. Martino, A. P. Caricato, and T. Tunno, “Acetone and ethanol solid-state gas sensors based on TiO2 nanoparticles thin film deposited by matrix assisted pulsed laser evaporation,” Sens. Actuators B, vol. 127, pp. 426-431, 2007.
[28] M. G. Manera, J. Spadavecchia, D. Buso, C. de Julian Fernandez, G. Mattei, A. Martucci, P. Mulvaney, J. Perez-Juste, R. Rella, L. Vasanelli, and P. Mazzoldi, “Optical gas sensing of TiO2 and TiO2/Au nanocomposite thin films,” Sens. Actuators B, vol. 132, pp. 107-115, 2008.
[29] H. F. Lu, F. Li, G. Liu, Z. G. Chen, D. W. Wang, H. T. Fang, G. Q. Lu, Z. H. Jiang, and H. M. Cheng, “Amorphous TiO2 nanotube arrays for low-temperature oxygen sensors,” Nanotechnology, vol. 19, pp. 405504-405511, 2008.
[30] H. Liu, D. Ding, C. Ning, and Z. Li, “Wide-range hydrogen sensing with Nb-doped TiO2 nanotubes,” Nanotechnology, vol. 23, pp. 015502-015507, 2012.
[31] V. Galstyan, E. Comini, G. Faglia, A. Vomiero, L. Borgese, E. Bontempi, and G. Sberveglieri, “Fabrication and investigation of gas sensing properties of Nb-doped TiO2 nanotubular arrays,” Nanotechnology, vol. 23, p. 235706, 2012.
[32] P. Hu, G. Du, W. Zhou, J. Cui, J. Lin, H. Liu, D. Liu, J. Wang, and S. Chen, “Enhancement of Ethanol Vapor Sensing of TiO2 Nanobelts by Surface Engineering,“ ACS Appl. Mater. Interfaces, vol. 2, pp. 3263-3269, 2010.
[33] H. W. Lin, Y. H. Chang, and C. Chen, “Facile Fabrication of TiO2 Nanorod Arrays for Gas Sensing using Double-Layered Anodic Oxidation Method,” J. Electrochem. Soc., vol. 159, pp. K5-K9, 2012.
[34] M. Epifani, T. Andreu, R. Zamani, J. Arbiol, E. Comini, P. Siciliano, G. Faglia, and J. R. Moranteb, “Pt doping triggers growth of TiO2 nanorods: nanocomposite synthesis and gas-sensing properties,” Cryst. Eng. Comm., vol. 14, pp. 3882-3887, 2012.
[35] L. Francioso, A. M. Taurino, A. Forleo, and P. Siciliano, “TiO2 nanowires array fabrication and gas sensing properties,” Sens. Actuators B, vol. 130, pp. 70-76, 2008.
[36] E. Comini, A. Cristalli, G. Faglia, and G. Sberveglieri, “Light enhanced gas sensing properties of indium oxide and tin dioxide sensors,” Sens. Actuators B, vol. 65, pp. 260-263, 2000.
[37] E. Comini, G. Faglia, and G. Sberveglieri, “UV light activation of tin oxide thin films for NO2 sensing at low temperatures,” Sens. Actuators B, vol. 78, pp. 73-77, 2001.
[38] K. Anothainart, M. Burgmair, A. Karthigeyan, M. Zimmer, and I. Eisele, “Light enhanced NO2 gas sensing with tin oxide at room temperature: conductance and work function measurements,” Sens. Actuators B, vol. 93, pp. 580-584, 2003.
[39] C. Ge, C. Xie, M. Hu, Y. Gui, Z. Bai, and D. Zeng, “Structural characteristics and UV-light enhanced gas sensitivity of La-doped ZnO nanoparticles,” Mater. Sci. Eng. B, vol. 141, pp. 43-48, 2007.
[40] B. de Lacy Costello, R. Ewen, N. M. Ratcliffe, and M. Richards, “Highly sensitive room temperature sensors based on the UV-LED activation of zinc oxide nanoparticles,” Sens. Actuators B, vol. 134, pp. 945-952, 2008.
[41] J. Gong, Y. H. Li, X. S. Chai, Z. S. Hu, and Y. L. Deng, “UV-light-activated ZnO fibers for organic gas sensing at room temperature,” J. Phys. Chem. C, vol. 114, pp. 1293-1298, 2010.
[42] J. M. Wu, H. C. Shih, W. T. Wu, Y. K. Tseng, and I. C. Chen, “Thermal evaporation growth and the luminescence property of TiO2 nanowires,” J Cryst Growth., vol. 281, pp. 384-390, 2005.
[43] T. J. Hsueh, C. L. Hsu, S. J. Chang, and I. C. Chen, “Laterally grown ZnO nanowire ethanol gas sensors,” Sens. Actuators B, vol. 126, pp. 473-477, 2007.
[44] D. Kohl, “The role of noble-metals in the chemistry of solid-state gas sensors,” Sens. Actuators B, vol. 1, pp. 158-162, 1990.
[45] P. P. Sahay, “Zinc oxide thin film gas sensor for detection of acetone,” J. Mater. Sci., vol. 40, pp. 4383-4385, 2005.
[46] X. Liu, B. Cheng, J. Hu, H. Qin, and M. Jiang, “Semiconducting gas sensor for ethanol based on LaMgxFe1−xO3 nanocrystals,” Sens. Actuators B, vol. 129, pp. 53-58, 2008.

Reference in chapter 5
[1] C. A. Spindt, “A thin film field emission cathode,” J. Appl. Phys., vol. 39, pp. 3504-3505, 1968.
[2] Y. H. Yang, C. X. Wang, B. Wang, N. S. Xu, and G. W. Yang, “ZnO nanowire and amorphous diamond nanocomposites and field emission enhancement,” Chem. Phys. Lett., vol. 403, pp. 248-251, 2005.
[3] M. S. Gudiksen, L. J. Lauhon, J. Wang, D. Smith, and C. M. Lieber, ”Growth of nanowire superlattice structures for nanoscale photonics and electronics,” Nature, vol. 415, pp. 617-620, 2002.
[4] Z. L. Wang and J. H. Song, “Piezoelectric nanogenerators based on zinc oxide nanowire arrays,” Science, vol. 312, pp. 242-246, 2006.
[5] A. H. MacDonald, “Copper oxides get charged up,” Nature, vol. 414, pp. 409-410, 2001.
[6] H. Fan, L. Yang, W. Hua, X. Wu, Z. Wu, S. Xie, and B. Zou, “Controlled synthesis of monodispersed CuO nanocrystals,” Nanotechnology, vol. 15, pp. 37-42, 2004.
[7] L. Liao, Z. Zhang, B. Yan, Z. Zheng, Q. L. Bao, T. Wu, and T. Yu, “Multifunctional CuO nanowire devices: P-type field effect transistors and CO gas sensors,” Nanotechnology, vol. 20, pp. 085203-085208, 2009.
[8] Y. W. Zhu, T. Yu, F. C. Cheong, X. J. Xu, and C. H. Sow, “Largescale synthesis and field emission properties of vertically oriented CuO nanowire films,” Nanotechnology, vol. 16, pp. 88-92, 2005.
[9] P. Saravanan, S. Alam, and G. N. Mathur, “A liquid-liquid interface technique to form films of CuO nanowhiskers,” Thin Solid Films, vol. 491, pp. 168-172, 2005.
[10] C. M. Tsai, G. D. Chen, T. C. Tseng, C. Y. Lee, C. T. Huang, W. Y. Tsai, W. C. Yang, and T. R. Yew, “CuO nanowire synthesis catalyzed by a CoWP nanofilter,” Acta Mater., vol. 57, pp. 1570-1576, 2009.
[11] X. Jiang, T. Herricks, and Y. Xia, “CuO nanowires can be synthesized by heating copper substrates in air,” Nano Lett., vol. 2, pp. 1333-1338, 2002.
[12] Y. Xia, P. Yang, Y. Sun, Y. Wu, B. Mayers, B. Gates, Y. Yin, and H. Yan, “One-dimensional nanostructures: Synthesis, characterization, applications,” Adv. Mater., vol. 15, pp. 353-389, 2003.
[13] C. L. Cheng, Y. R. Ma, M. H. Chou, C. Y. Huang, V. Yeh, and S. Y. Wu, “Direct observation of short-circuit diffusion during the formation of a single cupric oxide nanowire,” Nanotechnology, vol. 18, p. 245604, 2007.
[14] J. W. Shi, C. H. Jiang, K. M. Chen, J. L. Yen, and Y. J. Yang, “Single-mode vertical-cavity surface-emitting laser with ring-shaped light-emitting aperture,” Appl. Phys. Lett., vol. 87, p. 031109, 2005.
[15] C. L. Hsu, S. J. Chang, H. C. Hung, Y. R. Lin, C. J. Huang, Y. K. Tseng, and I. C. Chen, “Well-aligned, vertically Al-doped ZnO nanowires synthesized on ZnO:Ga/glass templates,” J. Electrochem. Soc., vol. 152, pp. G378-G381, 2005.
[16] C. A. Spindt, “A thin-film field-emission cathode,” J. Appl. Phys., vol. 39, pp. 3504-3505, 1968.
[17] Y. Huang, Z.Wang, Q. Wang, C. Gu, C. Tang, Y. Bando, and D. Golberg, ”Quasi-aligned Ga2O3 nanowires grown on brass wire meshes and their electrical and field-emission properties,” J. Phys. Chem. C, vol. 113, pp. 1980-1983, 2009.
[18] N. Singh, C. Yan, and P. S. Lee, “Room temperature CO gas sensing using Zn-doped In2O3 single nanowire field effect transistors,” Sens. Actuators B, vol. 150, pp. 19-24, 2010.
[19] M. S. Gudiksen, L. J. Lauhon, J. Wang, D. Smith, and C. M. Lieber, “Growth of nanowire superlattice structures for nanoscale photonics and electronics,” Nature, vol. 415, pp. 617-620, 2002.
[20] Z. L. Wang, and J. H. Song, “Piezoelectric nanogenerators based on zinc oxide nanowire arrays,” Science, vol. 312, pp. 242-246, 2006.
[21] S. J. Chang, C. S. Chang, Y. K. Su, R. W. Chuang, Y. C. Lin, S. C. Shei, H. M. Lo, H. Y. Lin, and J. C. Ke, “Highly reliable nitride-based LEDs with SPS + ITO upper contacts,” IEEE J. Quantum. Electron., vol. 39, pp. 1439-1443, 2003.
[22] S. J. Chang, C. H. Chen, P. C. Chang, Y. K. Su, P. C. Chen, Y. D. Jhou, H. Hung, S. M. Wang, and B. R. Luang, “Nitride-based LEDs with p-InGaN capping layer,” IEEE Trans. Electron. Dev., vol. 50, pp. 2567-2570, 2003.
[23] W. Y. Weng, T. J. Hsueh, S. S. Chang, S. S. Wang, H. T. Hsueh, and G. G. Huang, “A high-responsivity GaN nanowire UV photodetector,” IEEE J. Sel. Top. Quantum. Electron., vol. 17, pp. 996-1001, 2011.
[24] Y. Dong, B. Tian, T. J. Kempa, and C. M. Lieber, “Coaxial group III-nitride nanowire photovoltaics,” Nano Lett., vol. 9, pp. 2183-2187, 2009.
[25] J. C. Johnson, H. J. Choi, K. P. Knutsen, R. D. Schaller, P. Yang, and R. J. Saykally, “Single gallium nitride nanowire lasers,” Nature Mater., vol. 1, pp. 106-110, 2002.
[26] B. Ha, S. H. Seo, J. H. Cho, C. S. Yoon, J. Yoo, G. C. Yi, C. Y. Park, and C. J. Lee, “Optical and field emission properties of thin single-crystalline GaN nanowires,” J. Phys. Chem. B, vol. 109, pp. 11095-11099, 2005.
[27] C. T. Lin, G. H. Yu, X. Z. Wang, M. X. Cao, H. F. Lu, H. Gong, M. Qi, and A. Z. Li, “Catalyst-free growth of well vertically aligned GaN needlelike nanowire array with low-field electron emission properties,” J. Phys. Chem. C, vol. 112, pp. 18821-18824, 2008.
[28] V. Gottschalch, G. Wagner, J. Bauer, H. Paetzelt, and M. Shirnow, “VLS growth of GaN nanowires on various substrates,” J. Cryst. Growth, vol. 310, pp. 5123-5128, 2008.
[29] X. Zhou, J. Chesin, S. Crawford, and S. Gradecak, “Using seed particle composition to control structural and optical properties of GaN nanowires,” Nanotechnology, vol. 23, p. 285603, 2012.
[30] L.W. Tu, C. L. Hsiao, T. W. Chi, I. Lo, and K. Y. Hsieh, “Self-assembled vertical GaN nanorods grown by molecular-beam epitaxy,” App. Phys. Lett., vol. 82, pp. 1601-1603, 2003.
[31] L. Shekari, H. A. Hassan, S. M. Thahab, and Z. Hassan, “Growth and characterization of high-quality GaN nanowires on PZnO and PGaN by thermal evaporation,” J. Nanomater., vol. 2011, pp. 1-5, 2011.
[32] M. Zervos and A. Othonos, “Hydride-assisted growth of GaN nanowires on Au/Si(001) via the reaction of Ga with NH3 and H2,” J. Cryst. Growth, vol. 312, pp. 2631-3636, 2010.
[33] Y. M. Chang, M. L. Lin, T. Y. Lai, H. Y. Lee, C. M. Lin, Y. C. S. Wu, and J. Y. Juang, “Field emission properties of gold nanoparticledecorated ZnO nanopillars,” ACS Appl. Mater. Inter., vol. 4, pp. 6676-6682, 2012.
[34] W. Y. Weng, T. J. Hsueh, S. J. Chang, G. J. Huang, and S. P. Chang, “A solar-blind β-Ga2O3 nanowire photodetector,” IEEE Photon. Technol. Lett., vol. 22, pp. 709-711, 2010.
[35] S. J. Chang, T. J. Hsueh, I. C. Chen, S. F. Hsieh, S. P. Chang, C. L. Hsu, Y. R. Lin, and B. R. Huang, “Highly sensitive ZnO nanowire acetone vapor sensor with Au adsorption,” IEEE Trans. Nanotechnol., vol. 7, pp. 754-759, 2008.
[36] C. M. Balka¸s and R. F. Davis, “Synthesis routes and characterization of high-purity, single-phase gallium nitride powders,” J. Amer. Ceram. Soc., vol. 79, pp. 2309-2312, 1996.
[37] Z. H. Lan, C. H. Liang, C. W. Hsu, C. T. Wu, H. M. Lin, S. Dhara, K. H. Chen, L. C. Chen, and C. C. Chen, “Nanohomojunction GaN and nanoheterojunction InN nanorods on 1-D GaN nanowire substrate,” Adv. Funct. Mater., vol. 14, pp. 233-237, 2004.
[38] X. Y. Chen, C. T. Yip, M. K. Fung, A. B. Djuriši´c, and W. K. Chan, “GaN-nanowire-based dye-sensitized solar cells,” Appl. Phys. A, vol. 100, pp. 15-19, 2010.
[39] T. Y. Tsai, C. L. Hsu, S. J. Chang, S. I. Chen, H. T. Hsueh, and T. J. Hsueh, “Enhanced field electron emission from zinc-doped CuO nanowires,” IEEE Electron. Dev. Lett., vol. 33, pp. 887-889, 2012.
[40] C. C. Tang, X. W. Xu, L. Hu, and Y. X. Li, “Improving field emission properties of GaN nanowires by oxide coating,” Appl. Phys. Lett., vol. 94, p. 243105, 2009.